Creating a symbol that combines a number with a triangle for math-mode

Question

I'm trying to create a new symbol that simply combines a number with a triangle, by placing the number inside the triangle. It should work in math-mode (text mode would be nice, but not required).

I've tried the following:

\documentclass{article}
\usepackage{graphicx}


\newcommand{\trinum}[1]{%
\triangle\hspace{-.57em}\raisebox{0.1em}{\scalebox{.5}{#1}}
}

\begin{document}

Works fine in default environment
\[
\trinum{1} \qquad \trinum{2} \qquad \trinum{3}
\]

Slightly shifted when used in Huge environment:
{\Huge
\[
\trinum{1} \qquad \trinum{2} \qquad \trinum{3}
\]
}

Slightly shifted when used in tiny environment:
{\tiny % I know, it's too small to read, but just used as a check
\[
\trinum{1} \qquad \trinum{2} \qquad \trinum{3}
\]
}

Messed up when used as subscript or super script    
\[
\trinum{1} \qquad x_\trinum{1} \qquad x^\trinum{1}
\]

\end{document}

As you can see, it doesn't work nicely for scaled text and very badly for superscript and subscript. I was wondering if there is a better way of doing this.

Answer 1

Magic of \ooalign:

\documentclass{article}
\usepackage{graphicx}

\newcommand{\trinum}[1]{\mathpalette\dotrinum{#1}}
\newcommand{\dotrinum}[2]{{%
  \vphantom{\triangle}%
  \ooalign{%
    $#1\triangle$\cr\hidewidth\scaleraise{$#1#2$}\hidewidth\cr
  }%
}}
\newcommand{\scaleraise}[1]{%
  \raisebox{.2\height}{\scalebox{0.5}{#1}}%
}

\begin{document}

Works fine in default environment
\[
\trinum{1} \qquad \trinum{2} \qquad \trinum{3}
\]

Slightly shifted when used in Huge environment:
{\Huge
\[
\trinum{1} \qquad \trinum{2} \qquad \trinum{3}
\]
}

Slightly shifted when used in tiny environment:
{\tiny % I know, it's too small to read, but just used as a check
\[
\trinum{1} \qquad \trinum{2} \qquad \trinum{3}
\]
}

Messed up when used as subscript or super script    
\[
\trinum{1} \qquad x_{\trinum{1}} \qquad x^{\trinum{1}}
\]

\end{document}

I left your original text, except for bracing the subscript and superscript. See https://tex.stackexchange.com/a/22375/4427 for details on \ooalign

Answer 2

A TikZ solution with works in different sized for both math and text mode.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric}

\makeatletter
\newcommand*{\trinum}{}
\DeclareRobustCommand*{\trinum}[1]{%
  \ensuremath{%
    \mathpalette\@trinum{#1}%
  }%
}
\newdimen\trinum@sep
\newdimen\trinum@rule
\newcommand*{\@trinum}[2]{%
  % #1: math style
  % #2: num
  \settowidth\trinum@sep{$\m@th#1\mkern1mu$}%
  \setlength{\trinum@rule}{.8\trinum@sep}
  \tikz\node[
    regular polygon,
    regular polygon sides=3,
    draw,
    line width=\trinum@rule,
    inner sep=\trinum@sep,
  ]{$\m@th#1#2$};
}
\makeatother

\begin{document}
\[
  \trinum{1}\trinum{2}^{
    \trinum{1}\trinum{2}^{
     \trinum{1}\trinum{2}
    }
  }
\]
\begin{center}
  \Huge\trinum{2}
  \huge\trinum{2}
  \LARGE\trinum{2}
  \Large\trinum{2}
  \large\trinum{2}
  \normalsize\trinum{2}
  \small\trinum{2}
  \footnotesize\trinum{2}
  \scriptsize\trinum{2}
  \tiny\trinum{2}
\end{center}
\end{document}

Variation, the numbers can also be made smaller:

\newcommand*{\@trinum}[2]{%
  % #1: math style
  % #2: num
  \settowidth\trinum@sep{$\m@th#1\mkern.5mu$}%
  \settowidth{\trinum@rule}{$\m@th#1\mkern.8mu$}%
  \tikz\node[
    regular polygon,
    regular polygon sides=3,
    draw,
    line width=\trinum@rule,
    inner sep=\trinum@sep,
    scale=.5,
  ]{$\m@th#1#2$};
}